The invention relates to power supply systems, methods and computer program products for operation thereof and, more particularly, to uninterruptible power supply (UPS) systems, methods and computer program products for operation thereof.
UPSs may be coupled in parallel to a load to provide increased capacity and/or redundancy. For example, as illustrated in FIG. 1, a load 30 may be served by multiple UPSs 10 that are connected in common to the load 30, and which are configured to provide power to the load 30 from a primary source (e.g., a utility source) or, in the case of failure of the primary power source, from respective batteries 20. The UPSs 10 may communicate with one another via a communications bus 40 to allow interchange of control, status and other information.
In some parallel UPS systems, when operating on batteries, the runtime available to power the load may be constrained by the capacity of the weakest battery. For example, in the system illustrated in FIG. 1, when one of the UPSs 10 determines that its associated battery 20 has less than a predetermined capacity (e.g., has an undesirably low battery voltage), it may shut off, which may, in turn, cause the remaining UPSs 10 to shut down due to overload.